Axially engaging opposed clutch



July 18, 1950 w. v. THELANDER ETAL 2,515,277

AXIALLY ENGAGING oPPosED CLUTCH Filed Aug. 17, 1945 xg. V y

Patented July 1.8, 1950 ,AXIALLY ENGAGING OPPOSED CLUTCH`W.1Vincentlhelander.and Evcrson M. 'De Coursey, A'Auburn, `LInlL,.iassignora fby direct and mesne assignments, to fDana .vCornoraton,*Tolodo, QOhio, a 'c :orporation` of Virginia "Application -August 117,1945, SerialV No.'611;040

2.4. Claims. Il This invention relates toxfrictioniclutchesffor use.. onautomobilestractors, and .-otherzvehicles, andsuitablealso1fonindustrial-applications.

" The principal object of ourfinventien'isf'to vprovide simple .and fimprovedlanti-rattle means vfor usein'connectiontwithithe drive lugsonzthepressureiplate 'where these :lugsaproj ectfthrough/ openings i in:the back; plate, :whereby tofeliminate the hammer noise .f otherwiselproduced in the operation of .fthe clutch ,gasa :resultedthe operatingclearance necessarily yprovijde'dy for/ the f. drive; lugs,'inthefopenings inthe-'back plate.

According to fthe present invention, `small iwedgefshaped blocks,suitably mounted on the back :plate-in'the drive lugfopenings andarranged -to fhave abutment .with fthe drive lugs. on `4the coast side,are fnormally urged ainwagrddly -With ,respect j-to Athe axis ofrotation of heclutch by suitable f spring lmeans, @whereby tor Lafordample Working clearanceffor r the ,drive lugs Aini-said open- `ingsonlywhile` these.lyingwwedgesareiin retractediposition,theeclearance,however, being taken upautomatically:Whenrthe'lywheel,attains-arpredetermined, `.atvvlfiichthe1 flying=.wedg es move outwardly Figincler,` centrifugalAforce against the .acticmoi the spring means. and take l.1 1p., a1lclearance.

The invention 11s., illustrated in the accompanyingdrawing,` in -Whichz,.Eig. 1 .is -asectionthrough .afriction clutch embodying our.invention;

-Fig. .2 risfan enlarged,sectionaldetail. takeILon the line2-.2 of .Eig.l, showing-the relationship of the t flying wedge.. .o'f our inventionto `one of the .drive lugs onthe pressureplateiand onthelnefS-- of 1i,ieS-. 1, and. 2.

@The same, reference numerals vare applied 'to corresponding partsthroughout the views.

Referring iirst to Fig. 1, the reference numeral f4 is applied toaywheel mounted on' the rear end of the usual engine-crankshaftand-forming v.the driving element; the shaftf5-constituting thefdrivenelement Yand v extending-rreaiwardlylfrom the clutch into the gear boxof .theitransmission in'ethe clutch throwout bearing movable ;-in theVusual .Way lby meansof the clutch pedal Y.or lever (gnot shown) Theclutch .illustratediislke `that ,disclosed in ThelandenRatent 2,214,780,issued Septhepresentinvention is not limited tense, on that particularclutch but may be used on any friction clutch Where a similar .problemvof pro v idinganti- .rattle means is presentedythatis to say, in anyffriction. clutch wherein `the pressure .-plate -has ldrivelugsslidablyiengaged inopeningsin theiback plate: or .back platesegments, bearing 1in l.mind that `:in l the `learlier Thelander et a1.l:Patent 139855301, issued December-25, A`1934, the fr conventional backplate Wasfeliminatedin onefformfand .a number oiseparatebrackets'fastenedfto the'ly- `Wheel .were substitutedorming :what we have calleda'lever support. -The clutch herein :shown comprises 3a disk 1,;carried-.on a,hubu 8,lsp1ined on theifrontndothe f shafti ,.1 and a fpressure r plate -9 disposed .Qbehmdand inifconcentric:relation :to ithematted portion Hl fof thefdisk -1 to causeengagementthereo'f with theg-ilatjback .face I on thegilywheeL n.aoeordance with the Thelander.et-al.1I Pat ent ;1:;985,3 0l, .aplurality ofrrelease levers l 2are-prnvided `-,vs I- hich are arranged to -bevdelpressedagainsttheaction of compressicnfsprings |13 @by clutch pedalQperation. of the throyvgout 12.0 qbearinifagainstplie-:inner ends 14:-of thef levers .35 Fig. alsa. stilliurther .enlareedqsectional detail1:4 5 usual Way. Indicated at 6 is a DOItiQnY ofxthe .Q50 tember 17,1940, b ut it should be understood that .to disengage -the-.clu tch.-`'I Ahese levers are vpivot- .eed-fonfoloSS- pins trlearfthoirouterends lffto Ytransmit p r essuregcf thelsprings 13 in 4a multi- -plieddegree to .thevipressure plate v'9. Although:thefpressurerofzthe.;Springs isf multip1ied through the levers l2 forclutch engagement,4 there is an awreoiololol no.e@,1ia1f1.ia1iadvairline@.l inthe ,disengagement of th .lutoh,-=byreason.of the fatthat thesprings l -3 are closer tothe pivots I Sthan v-thefinner endsy1450i :the `.levers where the-throwvmit bearing ,6 yengages, .thusmaking for lighter pedalqaction The. arrangementalsois of advanftage from .the -standpoint V that there is very little loss 0`. SDr.-ing.pressureWhen the. clutch facings.y or ymats lll become worn,loeca usethere isfsdlittle ,-expansion,ioenmtted.of.the-:springsr in proportionto argiven amountv of Wear .of the facings. When the-levers. I2. are*depressed; and the springs i 3. are

accordingly, compressed `betv'veen the 1eve`rs|2 y and :the bank, plateor spider i,l, .the. pressurefplategg, ,in aceordance With..thedi sclosure in ,'Ifhelander Ratent, 2 21;4,70, is arranged to be.b'ackedaway from the flywheel 4 by hairpin typelsprings 18 acting,between the baclg plate 11 and .drivelugs l9 on.thepressureplatescthattheraisnolonger anytransmissionpf dlvetd the disk fl. The lugs f|.l9gnroieotirearwardly 'flfomfthe pressurerlatl, .parallentcth A znis.,of rotationnthe lnteh, and haveofit-,Sidegfaoesg and .321.substantally..por allelzltosorie anothere andetourafl 1ho the :pressure.plata whll. in the o .unmplOY-@df .clutch ,Slidblv vengage.tlne.osspf..site ides-ofss`1otsfo1eoee1 nesproe vided fin the rear Wall 2,21 ofthe-hack gplate lt 0 transmit ,drive from tnepnywheel (through the is atthese points that the hammer noise is produced which the anti-rattlemeans of our invention, indicated generally by the reference numeral 23,is desi-gned to eliminate, as will soon appear, the hammer noise beingproduced as a result of the working clearance necessarily provided inthe back plate slots or openings for the drive lugs.

The lugs I9 have set screws 24 threaded in longitudinal holes 25provided therein, and when the heads of the screws 24 are properlyadjusted relative to the outer ends I6 of the levers I2, lock nuts 26 onthe Shanks ofthe screws 24 are tightened against the rear .ends of thelugs I9 to lock the screws in adjusted position. In taking up for wearon the facings Ill, the screws 24 are backed up a turn or so after thelock nuts 26 are loosened, and When thevcorrect relationship of theclutch parts has been reproduced in that way, the screws 24 are lockedin adjusted position by tightening the nuts 26. These nuts serve toclamp the springs I8 by their middle U-shaped attaching portions 21,which straddle the screws 24; The legs 28 of the hairpin springs I8normally extend at an angle of approximately 45 with respect to oneanother, but are forced toward one another between the parallelrearwardly bent flanges 29 on the back plate, so that each spring I8affords a lateral component, due to the tendency of the legs 28 tospread apart,

`and a forward component, due to the extent of compression of the springin its assembled posi- -tion in the clutch. The lateral component, re-

sulting from the crowding of the legs 28 between 'the' anges 29, tendsto keep the associated lug I9 centralized with respect to' its slot oropening 30 in the back plate when the clutch is released, thus-minimizing the tendency toward rattling. The forward component, due tothe rearward `Adeflection of the legs 28 when the pressure plate 9 ismoved forward under spring action of the levers I2 in the engagement ofthe clutch, asserts itself when the clutch is released and causes thepressure plate 9 to be backed away from the flywheel and clutch disk asthe outer ends I6 of the levers I2 are retracted relative to taining thedesired gradual engagement of the clutch, the bosses 32 provided on theheads of the screws 24 and entered in center holes in these Aspringwashers serving to mount the washers on the 'screws and to take thedirect positive thrust of the levers I2 at full engagement of theclutch,

after the washers 3| have been compressed during initial engagement. Theouter ends I6 of the levers I2 are wide enough to engage the rimportions of the washers 3I at diametrically opposed points.

'The anti-rattle means 23 of our present invention consists of Wedgeblocks 33, which may be made in the form of die castings for cheapness,which are slidably mounted in the drive lug slots or openings providedin the back plate, there being one of these flying wedges associatedwith each drive lug on the "coast side 2 I, between the drive lugand theadjacent edge 34 of the opening. The edge 34 is in outwardly convergingrelation relative to the coast side 2l of the drive lug, speaking withreference to the axis of rotation of the clutch, the angle of v'agoodunderstanding of the objects and advantages of our invention. lhavebeen drawn to cover all legitimate modificad convergence being equal tothe angle of taper of the wedge 33, so that the wedge has uniformsurface engagement substantially its full length on the face 2I and edge34 when disposed in the operative position illustrated in Fig. 2.Flanges 35 extending the full length of the wedge 33 have slidableengagement on the inner and outer sides of the back wall 22 of the backplate, to prevent lateral displacement of the wedge from the opening 30while permitting freedom of endwise movement of the Wedge undercentrifugal force. A coiled compression spring 36 cooperates with eachwedge to urge the same normally inwardly toward the axis of rotation ofthe clutch to a retracted position in engagement with the inner edge 31of the opening 30, as indicated by the dotted line position of the wedgeshown in Fig. 2. The spring 36 ts in a recess 38 in the small end of thewedge and is compressed between the small end of the wedge and the outeredge 39 of the opening 30.

In operation, the flying wedges 33 are normally disposed in a retractedposition in abutment with the inner edges 31 of the openings 30, beingheld in that position under pressure of the springs 36 againstcentrifugal force acting on the wedges in the rotation of the flywheel.So long as the wedges are in a retracted position, ample workingclearance is left for the drive lugs I9 in the openings 30, and,consequently, there is nothing to interfere with the easy endwisemovement of the drive lugs in saidopenngs for engagement anddisengagement of the clutch. However, when the flywheel attains apredetermined speed of say 2000 R. P. M., the centrifugal force issufrlcient to cause the wedges 33 to move outwardly against the actionof the springs 36, so as to take up all clearance on the coast side 2Iof the drive lugs and accordingly keep the drive lugs in fixedengagement on their drive side 20 with the adjacent edges 40 of theopenings 38 in the back plate, whereby positively to eliminate anyrattling noise. Conversely, when the flywheel speed drops to apredetermined point, where the centrifugal force is less than thepressure of the springs 36, the wedges 33 are automatically retracted,thus allowing ample clearance again for freedom of'movement of the drivelugs I9 in the openings 30. It is, therefore, only during idling and atlow engine speeds, below the critical speed of say 2000 R. P. M., thatthe wedges 33 are retracted and the driving lugs I9 operate with ampleworking clearance in the openings 30, but at such times the springs I8can be relied upon to minimize, if not entirely eliminate, rattling.While we prefer to employ the springs 36, it should be understood thatthey are not absolutely essential and may be dispensed with if desired.

It is believed the foregoing description conveys The appended claimstions and adaptations.

We claim:

1. In a friction clutch comprising driving and driven elements, a backplate turning with the driving element, and a pressure plate for holdingsaid driving and driven elements drivingly engaged and'having one ormore drive projections thereon normally freely movable in one or moreopenings provided therefor in the back plate, a takeup element movablerelative to said projection in the aforesaid' opening positively kto ltake up i operating4 clearance; between; said. proj ectionIan-dropening.. i

2. .In a friction clutch comprising; 4driving( and driven elements, aback; plate turningwith the drivingl.element and a pressure plate .forholdn ing saiddriving and. driven elements drivingly engaged rand havingonefsor: more drive projections thereon normally freely movable in oneor more openings provided therefor in the back plate; .a takeupelementmovable under centrifu gal' force relative to said projection inthe.aforesaid opening positively to take up operating clearance between.said. projection and opening, and spr-ing meansznormally. tending tomove. .said takeup elementf to retracted. `positionalv which saidyprojection has a predeterminedoperating clear-ance in said openings,

3; In a friction clutch .comprisingdriving and driven elements,- abackplate turning with 'the driving element, and a pressurefvplate for.hold,- ing said driving and driven. elements drivingly engaged andhavingxone or more driveaprojections thereon normally freelyrnovableiinone. or'more openings provided thereforin the back`v plate, spring meansfor normally; centralizingI the pro'- ject-ion .in they opening, and atakenp.` element movable relative to said projectioninwthe aforesaidopening positively to take upl yoperating clearance between saidprojectionand opening;

4. In a friction clutch comprising driving'. and driven elements, a backlplate turning with the driving element, .antifa p-ressure-plate1-forholding said driving and driven elements drivinglyen;v gagedv and havingone or more driveprojections thereon normally freely movable in, one ormore openings provided thereforV in the back plate, spring means fornormally centralizing. the projection in theropening, a `takeupelement'4 movable under centrifugal forcerelative to said-.projection inthe aforesaid opening positively .to take up operatingv clearancebetween said/projection and opening, and spring means. normallyl tendingto move said takeup element to retracted position in which saidprojection has a predetermined operating clearancein said opening.

5. In a clutch comprising a: driving element and a driven element,av'pressure plate. fon holding the driving anddriven.elementsfrictionally engaged, a lever support mounted 4on thedriving element, a lever thereon arranged toacommunicate movement tothe'pressure plate under spring pressure to cause engagement of theclutch, spring means active against thev lever toiapply clutch engagingpressure to-thepnessureplate; said-pressure plate having-,av `projectionextending rearwardly through an` opening provided therefor in the lever:support toward the lever for operation of the pressure plate bythelever and to provide a-driving connection between the pressure plate andsadsupport, one-endl. of said lever being disposed in operative.Yrelation to said projection and the otherendoff saidileverbeing manuallyoperable to` release the clutchrandl a takeup element movable relativeto vsaid.y proj ection in the aforesaid openingpositivelyato. take upoperating clearance between the `projection and opening. y

6. In a clutch comprising a driving element and a driven element, apressure platefor'hold'- ing the driving and driven elementsfrictionally engaged, a lever support mountedfon. the driving element, alever thereon .arranged to communi cate movement to the pressureplate-under spring pressure to cause engagement ofithe. clutch; spring;means activeagainst theeleverf to. .apply :clutclfrn engaging pressure:to :the: pressuringplate; saidi pressure ,platefhaving aprojectionextend;- Aingr;reemwarlnlly: through: fan: opening:4 providedtherefor ini. the' lever supportv toward: Athef lever `for-operation.ofthe pressure. plate by the. lever amt toiprovidef a. driving connection.between the 'pressure plate andi` said support., onewendxofwsaid :leverbeinggdisposed in operative relation tofsaid projection .and the. otherend: or said:V leverbeing manually operabletox-release the clutch, atakeup element movable under-fcentrifugai forcerelativetofsaidypriojection in the aforesaid opening; posi*- ttvely totakerupopera-ting vclearance between the 4fprojectionfand opening,v andspring means nor.- mally' tending to move saidl takeup element tofalretracted position Lin which said pnojectionf'h'as a. predeterminedopera-ting. clearance. in- `said opening-.

-7. Inl` a: Vclutch comprising; eli-driving elementl andzadr-ivenelement, a pressure-plate fornholdingythe driving andidriven elements;.fnic-tionally engaged, ya ylever supporta mounted on thei drivingelement, a lever thereon .arrangedv tooommuniscatemovementto;thepressure-plate under:.spring pressure to. causeengagement'. of the clutch', spring-means active.. against lthe. leverVto apply clutch.- engaging. pressure: to the: pressure.- plate1saidrpnessure. .platef lhavingea projectionextend:- ingf rearwardlythroughy an' opening provided therefor .in thewlever` support toward4the lever for; operationofthefpressnre-.plate by. the-lever and'to-provide a driving vconnection between?, the pressure'plateandsaidsupport, one endcoffsaitl lever being disposed". in;l operativerela/tima@ft'oivsaidI projection. .andfthee other; zend of::saieliieverv being manuallyoperalole. to: Release* the" clutch, springmeans fora, normally" centralizing fthe. aforesaid proj ectioniintheaforesaid. opening, and; a rtaken-p elementv movable relative to` said.projection; in the aforesaidfopening to takerup OperatingcIearance;between the projection. and opening..

.8.a Inn-'ae cl-utch. comprising .rai driving.` element andi a driven`element; .a 'pressure plate.: for:- hold#- ings; the;A driving and;ydriven: .elements friction'a'lly engaged; :a1.le.verrxsupportvmountedfon the driving element.. a leverfthereon arranged: to;communicate-.movement to the. pressure plate. under spring pressure.'to! cause engagement' of the. clutch, spring'. means. activ-e2 .againstthe leverl to: apply clutch; engaging. pressure; 'to the pressure plate,said: pressure. plate; having, a projection `extermiing. rearwardlythrough an opening. provided thereforrin the leven support towardsth'elever :forroperaticn: ofi the v.press-ureA plate by the' y levierand.to.fp1tovidei a driving: f connection rbet'ween the press-ure.yplate vandlsaidfsujznport,.onerend of said lever being disposed..inioperativef relationito said projection;andl;.the;y otherl endrl ofisaid. lever being manuaily operah'lef etorelease the clutch', springmeans for; normally. `centraiizing;y therl aforesaid projection-rim the;aforesaid! opening. an takeup element movable:l under centrifugalforcerelative to said projectioniin'tne.aforesaidlopening'to-.take.upenoperating clearances.. between the projection and opening;andxspri-n-g-meansanormally tend; ingritoi move vsaid .t'akeupi element4to.l a. .retracted positionrlnl which said-.z proj ection'. has afpi'edeteri mined operating clearance inrsaidlopening: `9.. In.arfrictionz clutchzcomprisingi a nywheel serving; as.z ya'..;driving:element, and i la..- :lutch dislry serwiiiggas fa.adrivenelementiV aipressure plate-f o1* holding ;the-'fclutch disk lfmctionally;engagedwith thecglytvlrreel, said: plateihawingia. plure'rlity` ofcircumferentiallyf spaced drive: ylugs# projecting reax'wandly.Ttherefrom; .lever :supporting means i'nountedi.y von A the flywheel' andslidably/engaged by. said lugs whereby to :transmitdrive from theflywheel to thepressureplate while permitting movementof thelflattertoward andaway from the flywheel, said lever supporting meansprovidinglaterally spaced supporting walls on opposite sides ofeach of said drivelugs, Aa release lever pivotally supported near itslouter endbetweensaid walls adjacent each of said lugs'v with the outerenddisposed inoperative relation to the lug to transmit pressure tothepressure plate, springs supported o'n said lever supporting means andfengaging said levers between the pivots therefor and their inner ends,said levers being operable manually at their inner ends to releasespring pressure from the pressure plate, springs means cooperating withthe :aforesaid projection land the aforesaid supporting walls on theleverA supporting means to centralize the projection in the aforesaidopening, and a takeup element movablerelative to said projection in theaforesaid opening to take up operating clearance between the Aprojectionand opening. y y

10. In a friction clutch comprising a vflywheel serving as a drivingelement, andaclutchldisk serving as a driven element, a pressure platefor holding the clutch disk frictionally engaged with the flywheel, saidplate having a plurality of circumferentially spaced drive lugsprojecting rearwardly therefrom, lever supporting means mounted on theflywheel and slidably engaged by said lugs whereby to transmit drivefrom the flywheel to the pressure plate while permitting movement of the-latter toward and away from the flywheel, said lever` supporting meansproviding laterally spaced supporting walls `on opposite sides of eachof` said drive'lugs, a release lever pivotally supported near its outerendv between said walls adjacent each of said lugs with the outer enddisposed in operative relation to the lug to Ytransmit pressure to thepressure plate, springs supported on said lever supporting meansand-.engaging said levers between' the pivots therefor and their innerends, said levers being operable manually at theirinner ends to releasespring pressure from the pressure plate, spring means cooperating withthe aforesaid projection and the vaforesaid supporting walls on thelever supporting means to centralize the projection in the aforesaidopening, a takeup element movable under centrifugal force relative tosaid projection inthe aforesaidV opening to take up operatingclearancebetween the projection and opening, and spring means normally tending tomove said takeup element to a retracted position in which saidprojection has a predetermined operating clearance in said opening. 11.In a friction clutch comprising driving and driven elements, a backplate turning with the driving element, and a pressure plate for holdingsaid driving and driven elements drivingly engaged and having one ormore drive projectionsthereon. normally freely movable in one or more'openings provided therefor in the back plate, awedge movable relativeto the coast side of said projection in the aforesaid opening to take upoperating clearance .between said` projection-and opening.

12. In a friction clutch comprising driving and driven elements, a backplate turning with the driving element, and aipressure plate for holding.said driving and driven elements drivingly engaged and having one ormore drive projections thereon normally freelyV movable in one'ormoreaopeningsprovided therefore in 'the back 8. plate, a wedge movableunder centrifugal force relative to the coast side ofsaid projection inthe aforesaid opening to take up operating clearance between saidprojection and opening, and spring means normally tending to move saidwedge to retracted position in which said projection has a predeterminedoperating clearance in said opening.

13. In a friction clutch comprising driving and driven elements, a backplate turning with the driving element, and a pressure plate for holdingsaid driving and driven elements drivingly engaged and having one ormore drive projections thereonv normally freely movable in one or moreopenings provided therefor in the back plate, spring means for normallycentralizing the projection in the opening, and a Wedge movable relative,to the coast side of said projection in the aforesaid opening to takeup operating clearance between said projection and opening.

14. In a friction clutch comprising driving and driven elements, a backplate turning with the driving element, and a pressure plate for holdingsaid driving and ydriven elements drivingly engaged and having one ormore drive projections thereon normally freely movable in one or moreopenings provided therefor in the back plate, spring means for normallycentralizing the projection in the opening, a wedge movable undercentrifugal force relative to the coast side of said projection in theaforesaid opening to take up operating clearance between said projectionand opening, and spring means normally tending to move said wedge toretracted position in which said projection has a, predeterminedoperating clearance in said opening.

15. In a friction clutch comprising driving and driven elements, abackplate turning with the driving-element, and a pressure plate for holdingsaid driving and'driven 'elements drivingly engaged and having one ormore drive projections thereon normally freely movable in one or moreopenings provided therefor in the back plate, a wedge of channel-shapedcross-section slidably guided by engagement 0f one edge portion of theopening in the channel of the wedge for movement relative to one ofthecoast and drive sides of said projection t'o take up operating clearancebetween said projection and opening.

16. A clutch structure as set forth in claim 15, wherein said Wedge isarranged to move toward takeup position under centrifugal force, saidstructure including spring' means for returning the wedge to retractedposition.

17. In a friction clutch comprising a, back plate, and a pressure platehaving a drive lug projecting therefrom freely through an openingprovided in the back plate, a wedge for application to the edge portionof the back plate in said opening on one of the coast and drive sides ofsaid drive lug, -said wedge being of elongated form and channel-shapedin cross-section to accommodate in the channel thereof that portion ofthe back plate next to the opening as a guide and support for the wedge,the length of said wedge being less than the length of the edge portionon which said wedge operates, and the channel therein being of a widthslightly greaterv than the thickness of said edge portion.

18. In va friction clutch comprising a back plate, and a pressure platehaving a drive lug projecting therefrom freely through an openingprovided in the back plate, a wedge for application to the edge portionof the back plate in'said opening on one of the coast and drive sides ofsaid drive lug, said wedge being of elongated form and channel-shaped incross-section to accommodate in the channel thereof that portion of theback plate next to the opening as a guide and support for the wedge, thelength of said wedge being less than the length of the edge portion onwhich said wedge operates, and the channel therein being of a widthslightly greater than the thickness of said edge portion, said wedgebeing cast substantially to the form described.

19. In a friction clutch comprising driving and driven elements, a backplate turning with the driving element, and a pressure plate for holdingsaid driving and driven elements drivingly engaged and having one ormore drive projections thereon normally freely movable in one or moreopenings provided therefor in the back plate, a single spring meanscooperating with the projection for normally centralizing the projectionin the opening and urging the pressure plate to retracted position, anda, takeup element movable relative to said projection in the aforesaidopening positively to take up operating clearance between saidprojection and opening.

20. In a friction clutch comprising driving and driven elements, a backplate turning with the driving element, and a pressure plate for holdingsaid driving and driven elements drivingly engaged and having one ormore drive projections thereon normally freely movable in one or moreopenings provided therefor in the back plate, a single spring meanscooperating with the projection for normally centralizing the projectionin the opening and urging the pressure plate to retracted position, atakeup element movable under centrifugal force relative to saidprojection in the aforesaid opening positively to take up operatingclearance between said projection and opening, and spring means normallytending to move said takeup element to retracted position in which saidprojection has a predetermined operating clearance in said opening.

21. In a friction clutch comprising driving and driven elements, a backplate turning with the driving element, and a pressure plate for holdingsaid driving and driven elements drivingly engaged and having one ormore drive projections thereon normally freely movable in one or moreopenings provided therefor in the back plate, a single spring meanscooperating with the projection for normally centralizing the projectionin the opening and urging the pressure plate to retracted position, anda Wedge movable relative to the coast side of said projection in theaforesaid opening to take up operating clearance between said projectionand opening.

22. In a friction clutch comprising driving and driven elements, a backplate turning with the driving element, and a pressure plate for holdingsaid driving and driven elements drivingly engaged and having one ormore drive projections thereon normally freely movable in one or moreopenings provided therefor in the back plate, a single spring meanscooperating with the projection for normally centralizing the projectionin the opening and urging the pressure plate to retracted position, awedge movable under centrifugal force relative to the coast side of saidprojection in the aforesaid opening to take up operating clearancebetween said projection and opening, and spring means normally tendingto move said wedge to retracted position in which said projection has apredetermined operating clearance in said opening.

23. In a friction clutch comprising driving and driven elements, a backplate turning with the driving element, and a pressure plate for holdingsaid driving and driven elements drivingly engaged and having one ormore drive projections thereon normally freely movable in one or moreopenings provided therefor in the back plate, a single spring meanscooperating with the projection for normally centralizing the projectionin the opening and urging the pressure plate to retracted position, awedge of channel-shaped cross-section slidably guided by engagement ofone edge portion of the opening in the channel of the wedge for movementrelative to one of the coast and drive sides of said projection to takeup operating clearance between said projection and opening.

24. A clutch structure as set forth in claim 23, wherein said wedge isarranged to move toward takeup position under centrifugal force, saidstructure including spring means for returning the wedge to retractedposition.

W. VINCENT THELANDER. EVERSON M. DE COURSEY.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,639,379 La Londe Aug. 16, 19272,214,780 Thelander Sept. 1'?, 1940

